PHILADELPHIA  Americans are less interested in spending time in natural surroundings like national parks because they are spending more time watching television, playing video games and surfing the Internet, according to a study released Tuesday.

The study, for The Nature Conservancy, found per-capita visits to national parks have been declining for years.

National park visitation data starting in 1930 peaked in 1987 at 1.2 visits per person per year. But by 2003 it had declined by about 25 percent to 0.9 visits per person per year, said Oliver Pergams, an ecologist at the University of Illinois who analyzed the data for the study.

The data, based on government statistics and other sources, were taken as a proxy for interest in nature in general.

Researchers tested more than two dozen possible explanations for the trend and found that 98 percent of the drop in national park visits was explained by video games, movie rentals, going out to movies, Internet use and rising fuel prices.

Other possible explanations such as family income or the aging population were ruled out.

There was a sufficiently high correlation between declining national park visits and the burgeoning use of electronic media that led Pergams and his associate, Patricia Zaradic, believe the two are linked. "It made us feel fairly certain that there is an association," Pergams told Reuters.

The study, to be published in the Journal of Environmental Management, concludes that the trend has negative implications for environmental stewardship.

"We may be seeing evidence of a fundamental shift away from people's appreciation of nature to 'videophilia' which we here define as the new human tendency to focus on sedentary activities involving electronic media," the researchers said.

"Such a shift would not bode well for the future of biodiversity conservation."

Nature Conservancy President Steve McCormick said the study suggests Americans and their children in particular are losing their connection to the natural world.

"When children choose TVs over trees, they lose touch with the physical world outside and the fundamental connection of those places to our daily lives," McCormick said.